This project is designed to investigate the spatial distribution and functional properties of cortical neuron "colonies" in the primate motor cortex that project to the spinal cord and are associated with individual muscles or closely related groups of muscles, as well as the activity of neurons in such colonies during defined voluntary motor behaviors. Cortical cell discharge patterns during normal movements are evaluated in terms of EMG patterns, and their responses to small loading and unloading torque perturbations. These responses are evaluated before, during and after cooling of the supplementary motor area. Spinal cord location of motoneurons innervating selected forelimb muscles and termination patterns in the spinal cord and brain stem of sensory receptors within these muscles are studied using anterograde and retrograde tracing methods.